1. Field of the Invention
The present invention relates to an integrated circuit mounted board, a printed wiring board, and a method of manufacturing an integrated circuit mounted board.
2. Description of the Related Art
In a conventional integrated circuit mounted board, a bare chip of an integrated circuit made of semiconductor such as, for example, silicon is mounted on a printed wiring board. In the printed circuit board, insulating layers made of an insulating material and a wiring pattern including conductive lines made of, for example, copper are disposed on a metal base.
In a general method of manufacturing the integrated circuit mounted board, a wire bonding connection or a flip-chip connection may be performed. In the wire bonding connection, pads of the bare chip and electrodes of the wiring pattern are bonded through conductive wires. In the flip-chip connection, the integrated circuit is bonded on the printed wiring board through bumps formed on pads of the bare chip.
When gold is used as the conductive wires or the bumps (hereafter, called connecting medium) in the wire bonding connection or the flip-chip connection, an ultrasonic wave thermocompression method may be used. In the ultrasonic wave thermocompression method, the printed wiring board is mounted on a heat stage (ceramic or metal) heated at a temperature from 150° C. to 200° C. and an ultrasonic wave vibration is applied to the connecting medium on the printed wiring board.
In an integrated circuit mounted board, glass epoxy resin or a phenol paper is commonly used as an insulating material. When an integrated circuit mounted board is used for dealing a high frequency signal such as millimeter wave, fluorine resin such as, for example, polytetrafluoroethylene (PTFE) having a lower dielectric loss tangent than the above-described insulating material can be used as described, for example, in JP-A-7-323501. By using an insulating material having a low dielectric loss tangent, energy loss (dielectric loss) which is proportional to a signal frequency and the dielectric loss tangent can be restricted.
An elastic modulus of an insulating material such as, for example, fluorine resin and liquid crystal polymer (LCP) suitably used for dealing high frequency may drastically reduce at a high temperature from 150° C. to 200° C.
Thus, when the wire bonding connection and the flip-chip bonding is performed during a manufacturing process of the integrated circuit mounted board, the insulating material included in the printed wiring board on the heat stage may disperse ultrasonic wave and load applied to the connecting medium. As a result, the wire bonding connection or the flip-chip connection may be improperly performed, and a reliability of the integrated circuit mounted board may be reduced.